JP2017157830A - Piezoelectric ceramic plate, plate-like substrate, and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic plate, a plate-like substrate, and an electronic component which are less deformed by firing.SOLUTION: The piezoelectric ceramic plate whose principle surface is circular includes a plurality of crystal grains, a pair of principal surfaces 1c and side surfaces. At least one of side surfaces 1d and 1h are baked-up faces. When an average particle diameter of crystal grains located in the vicinity of a surface center of gravity G of the principle surfaces 1c is denoted as D1, and an average grain size of the crystal grains located in the vicinity of the side surfaces 1d and 1h as the baked-up face is denoted as D2, a ratio of D2 to D1 (D2/D1) is in a range of 0.9 to 1.1.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a piezoelectric ceramic plate, a plate-like substrate, and an electronic component.

  Piezoelectric ceramic plates are used in various electronic components such as piezoelectric actuators that use displacement and force generated through a piezoelectric phenomenon as a mechanical drive source. As the use of piezoelectric actuators expands, multilayer piezoelectric actuators that can obtain larger displacement and generated force at a lower voltage have been increasingly used.

  Conventionally, since the deformation (shrinkage variation) of the piezoelectric ceramic plate after firing was large, processing such as cutting and polishing of the piezoelectric ceramic plate was performed after firing in order to control the shape and dimensions of the piezoelectric ceramic plate within a predetermined range. (For example, see Patent Document 1).

Japanese Patent Laid-Open No. 3-54878

  However, conventionally, as described above, since the shape and dimensions of the piezoelectric ceramic plate were controlled after being fired in order to control the shape and dimensions of the piezoelectric ceramic plate, the number of processes was increased and the manufacturing cost was increased. There was a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric ceramic plate, a plate-like substrate, and an electronic component that are less deformed in a baked state and can reduce processing after firing.

  The piezoelectric ceramic plate of the present invention has a plurality of crystal grains, and has a pair of main surfaces and a side surface located between the main surfaces, at least one of the side surfaces being a baked surface, and the center of gravity of the main surface. When the average particle diameter of the crystal particles located in the vicinity is D1, and the average particle diameter of the crystal particles located in the vicinity of the side surface that is the baked surface is D2, the ratio of D2 to D1 (D2 / D1) is: It is in the range of 0.9 to 1.1.

  The plate-like substrate of the present invention has an internal electrode in the piezoelectric ceramic plate.

  The electronic component according to the present invention includes a surface electrode disposed on the surface of the plate-like substrate and a via hole connected to the internal electrode and extending in the thickness direction of the piezoelectric ceramic plate and drawn to the surface of the plate-like substrate. And a conductor.

  An electronic component according to the present invention includes the plate-shaped substrate and an external electrode connected to the internal electrode, and the piezoelectric ceramic plate includes the side surface having a processing surface, and the processing surface includes the side surface. External electrodes are arranged.

  According to the piezoelectric ceramic plate of the present invention, deformation of the piezoelectric ceramic plate is small, and processing after firing can be reduced. Moreover, according to the plate-shaped substrate and electronic component of the present invention, the manufacturing cost can be reduced.

FIG. 2 shows a piezoelectric ceramic plate, in which (a) is a perspective view in the case of having a rectangular main surface, and (b) is a perspective view in the case of having a circular main surface. (A) is explanatory drawing which shows the structure | tissue of a piezoelectric ceramic, (b) is a scanning electron micrograph which shows an example of the surface from a side surface to a main surface. In order to explain the measurement position of the crystal grain size, (a) is a plan view of a piezoelectric ceramic plate having a rectangular main surface, and (b) is a plan view of a piezoelectric ceramic plate having a circular main surface. The amount of deformation of the piezoelectric ceramic plate will be described. (A) is a plan view of a piezoelectric ceramic plate having a substantially rectangular main surface, and (b) is a plan view of a piezoelectric ceramic plate having a trapezoidal main surface. It is explanatory drawing regarding flatness. BRIEF DESCRIPTION OF THE DRAWINGS 1st Embodiment of an electronic component is shown typically, (a) is a schematic plan view, (b) is the sectional view on the AA line of (a). The 2nd Embodiment of an electronic component is shown, (a) is a schematic longitudinal cross-sectional view, (b) is a schematic cross-sectional view.

(Piezoelectric plate)
A piezoelectric ceramic plate 1 shown in FIG. 1A includes a pair of rectangular main surfaces 1c having a pair of substantially parallel sides 1a facing each other, another pair of sides 1b, a pair of first side surfaces 1d facing each other, and It has a pair of 2nd side surface 1e which opposes. The side on the main surface 1c side that constitutes the pair of first side surfaces 1d is the side 1a of the main surface 1c. Thereby, a pair of 1st side surfaces 1d are substantially parallel.

  The piezoelectric ceramic plate 1 shown in FIG. 1B has a pair of circular main surfaces 1c, and a side surface 1h that connects an outer periphery 1f of one main surface 1c and an outer periphery 1g of the other main surface 1c. Yes.

  The piezoelectric ceramic plate 1 has a plurality of crystal grains 2 and crystal grain boundaries 3 existing between the crystal grains 2 as shown in FIG.

  A pair of main surfaces 1c and a pair of first side surfaces 1d in FIG. 1 (a) and a pair of main surfaces 1c and side surfaces 1h in FIG. 1 (b) are baked surfaces as shown in FIG. 2 (b). . In FIG. 2B, the surface of the piezoelectric ceramic plate 1 shown in FIG. 1A is observed from obliquely above the main surface 1c so that the rectangular main surface 1c and the first side surface 1d can be confirmed. It is the transmission electron microscope (SEM) photograph which carried out.

  As shown in FIG. 2B, the baked surface is a surface that is not cut or polished after firing. In the form shown in FIG. 2B, the pair of second side surfaces 1e and the pair of main surfaces 1c are also baked surfaces, and the entire circumference is a baked surface. A side that is a baked surface is simply called a baked side.

  3 (a) and 3 (b), the average particle diameter of the crystal particles 2 located in the vicinity of the surface gravity center G of the main surface 1c (inside the region surrounded by the alternate long and short dash line) is D1, and the baked side surface Let D2 be the average particle diameter of the crystal grains 2 located in the vicinity of (1d, 1h) (outside the area surrounded by the broken line). In the piezoelectric ceramic plate 1 of the present embodiment, the ratio of D2 to D1 (D2 / D1) is in the range of 0.9 to 1.1.

  Here, the vicinity of the surface gravity center G of the main surface 1c is a region where the distance Lg from the surface gravity center G is within 50% of the distance Lo between the surface gravity center G and the baked side surfaces (1d, 1h). The vicinity of the baked side surface (1d, 1h) is a region where the distance Lf from the surface centroid G is 90% or more with respect to the distance Lo between the surface centroid G and the baked side surface (1d, 1h). .

The average particle diameter of the crystal particles 2 is determined by, for example, scanning a cross section or surface of the piezoelectric ceramic plate 1 with a scanning electron microscope (
For example, the image may be calculated by observing with a SEM) at a magnification of, for example, 3000 times and processing the photographed image. The cross section or surface of the piezoelectric ceramic plate 1 may be subjected to processing such as polishing and grain boundary etching (thermal etching, chemical etching) as necessary.

  Note that D1 may be measured for at least a part of the vicinity of the center of gravity G of the main surface 1c, and D2 may be measured for at least a part of the vicinity of the baked side surface. In addition, when the piezoelectric ceramic plate 1 has a plurality of baked side surfaces, the average particle diameter is measured for at least a part of the region near each baked side surface, and the average of the average particle size may be D2.

  In other words, in the piezoelectric ceramic plate 1 of the present embodiment, the average particle diameter of the crystal particles 2 is uniform regardless of the measurement position. That is, since the entire piezoelectric ceramic plate 1 is uniformly sintered, deformation due to the difference in the sintered state (firing shrinkage) is small. Therefore, the piezoelectric ceramic plate 1 having a precise shape and dimensions can be obtained easily without being cut or polished. As a result, the manufacturing cost can be reduced. Moreover, since processing is not required after firing, breakage such as chipping or cracking of the thin piezoelectric ceramic plate 1 can be reduced.

<Deformation in the surface direction>
The piezoelectric ceramic plate 1 of the present embodiment has a small deformation in the surface direction (xy direction) of the main surface 1c. For example, as shown in FIG. 4 (a), a pair of first side surfaces at the center in the length direction (x-axis direction) of the first side surface 1d of the piezoceramic plate 1 having a square main surface 1c as a baked side surface. The length between 1d is Lc, the length between a pair of first side surfaces 1d at the end in the length direction (x-axis direction) of the first side surface 1d is Le, and the difference between Le and Lc is ΔL. At this time, in the piezoelectric ceramic plate 1 of the present embodiment, the ratio of ΔL to Lc (ΔL / Lc) can be 1.0% or less, 0.2% or less, particularly 0.1% or less.

  The difference ΔL is a value obtained by subtracting the shorter one from the longer one so as to be a positive value, that is, the absolute value of the difference between Le and Lc. The length between the first side surfaces 1d can be measured by, for example, a caliper or an image size measuring device (such as a CNC image measuring device).

  Specifically, as shown by a two-dot chain line in FIG. 4A, a straight line connecting both ends of one side 1a of the main surface 1c of the piezoelectric ceramic plate 1 is drawn, and both ends of the side 1a on this straight line are drawn. A perpendicular line C (one-dot chain line) is drawn with respect to the middle point, a point where the perpendicular line C intersects with a pair of sides 1a on the main surface 1c is obtained, and a length between these intersecting points is defined as Lc. Further, a line E that is located at either end of one side 1a and is parallel to the perpendicular C is drawn, and a point where the line E intersects with the pair of sides 1a is obtained, and the length between these intersecting points is determined. Let Le be Le.

<Deformation in the thickness direction>
Further, the piezoelectric ceramic plate 1 of the present embodiment has a small warpage and excellent flatness, that is, a deformation in the thickness direction (z direction) is small. The flatness is a numerical value (ΔF / Lmax) obtained by measuring the shape (unevenness) of the entire main surface 1c, defining the difference between the maximum value and the minimum value as ΔF, and ΔF being normalized by the maximum length Lmax of the main surface. (See FIG. 5). In the piezoelectric ceramic plate 1 of the present embodiment, the flatness can be 0.2% or less, particularly 0.1% or less. The difference ΔF is a value obtained by subtracting the minimum value from the maximum value of the unevenness. The shape (unevenness) of the entire main surface 1c can be measured by, for example, a laser three-dimensional measuring device.

When the ratio of D2 to D1 (D2 / D1) is smaller than 0.9 or larger than 1.1, the sintered state of the piezoelectric ceramic plate 1 is not uniform, and deformation tends to increase. In the conventional piezoelectric ceramic plate 1, there is a tendency that the center of the main surface 1c is easy to sinter and the outside is difficult to sinter. That is, the conventional piezoelectric ceramic plate 1 has a large particle size near the center of the main surface 1c, that is, near the center of gravity G, and a small particle size near the outside, that is, near the baked side surface, and D2 / D1 tends to be smaller than 0.9. was there.

  This is because the vapor pressure of components that promote the sintering contained in the conventional piezoelectric ceramic plate 1 is high, and these components are easily detached from the surface of the piezoelectric ceramic plate 1 during the sintering process. In particular, in addition to the main surface 1c, in the vicinity of these side surfaces adjacent to the side surfaces 1d, 1e, and 1h, the components that promote sintering are desorbed not only from the main surface 1c but also from these side surfaces. As a result, sintering progressed near the center of gravity G of the surface and grain growth occurred, and no grain growth occurred near the side surface, and D2 / D1 was smaller than 0.9. This is due to the fact that the above-mentioned component that promotes sintering causes the liquid phase generation temperature to shift due to subtle differences in the composition, so that time is required for sintering, and the above distribution is generated in the liquid phase distribution. Conceivable.

  If such a conventional piezoelectric ceramic plate 1 is rectangular, for example, ΔL / Lc is larger than 1%, the deformation is large, and the shape needs to be adjusted by side processing.

  In addition, such a conventional piezoelectric ceramic plate 1 has a flatness ΔF / Lmax larger than 0.2%, for example, and is damaged when bonded to other members or has desired characteristics due to stress generated by the bonding. It may not be obtained.

  In addition, although Fig.1 (a) demonstrated the piezoelectric ceramic board 1 which has a pair of rectangular main surfaces 1c, as shown in FIG.4 (b), the piezoelectric ceramic which has a pair of trapezoid main surfaces 1c. Of course, it may be the piezoelectric ceramic plate 1 having the plate 1 or a pair of other polygonal main surfaces 1c. Further, FIG. 1B illustrates the piezoelectric ceramic plate 1 having a pair of circular main surfaces 1c. For example, the piezoelectric ceramic plate 1 having a pair of main surfaces 1c having an elliptical shape, a semicircular shape, and an indefinite shape. Of course, it may be.

  Moreover, although FIG. 1 demonstrated the case where a pair of main surface 1c was a baking surface, it does not need to be a baking surface. By making the pair of main surfaces 1c baked surfaces, it is possible to eliminate the processing of the main surface 1c of the piezoelectric ceramic plate 1 after firing.

Further, the piezoelectric ceramic plate 1 has (D2 / D1) in the range of 0.9 to 1.1 even when the area of the main surface 1c is 360 mm ² or more, and further, the area of the main surface 1c is 1000 mm. Even when it is ² or more, (D2 / D1) is preferably in the range of 0.9 to 1.1. Furthermore, when the piezoelectric ceramic plate 1 does not have an internal electrode, the area of the main surface 1c is 360 mm ² or more, further 1000 mm ² or more as described above, and the thickness is 50 μm or less, and further 30 μm or less. Even in this case, it is preferable that (D2 / D1) is in the range of 0.9 to 1.1.

(Plate substrate, electronic parts)
FIG. 6 shows a first embodiment of an electronic component. This electronic component includes a plate-like substrate 8 having an internal electrode 5 in a piezoelectric ceramic plate 1. A plurality of surface electrodes 10 formed on the surface of the plate-like substrate 8 and via-hole conductors 11 are provided. The via-hole conductor 11 is connected to the internal electrode 5, extends in the thickness direction (z-axis direction) of the piezoelectric ceramic plate 1, and is drawn to the surface of the plate-like substrate 8. In the piezoelectric ceramic plate 1, the pair of first side surfaces 1d and the pair of second side surfaces 1e are baked surfaces, respectively.

That is, in the first embodiment, the first side surface 1d and the second side surface 1e of the piezoelectric ceramic plate 1 are baked surfaces, and the main surface 1c of the piezoelectric ceramic plate 1 is also a baked surface. The side surfaces 1d and 1e of the piezoelectric ceramic plate 1 are configured by the two side surfaces of the piezoelectric ceramic layer 9, but cannot be confirmed from the outside, and the side surfaces 1d and 1e of the piezoelectric ceramic plate 1 are integrally formed. It is composed. Since the boundary of the piezoelectric ceramic layer 9 is the internal electrode 5, the number of piezoelectric ceramic layers 9 can be confirmed by the number of stacked internal electrodes 5.

  In such an electronic component, a voltage is applied between the surface electrode 10 and the internal electrode 5 via the via-hole conductor 11 drawn to the surface of the plate-like substrate 8 and the surface electrode 10. In FIG. 6A, the illustration of the via-hole conductor 11 is omitted.

The area of the main surface 1c of the piezoelectric ceramic plate 1 is 360 mm ² or more, further 1000 mm ² or more, and the thickness of the piezoelectric ceramic plate 1 having the internal electrode 5 is 150 μm or less, 100 μm or less, 60 μm or less, Furthermore, it is 50 μm or less. Further, the area of the internal electrode 5 in plan view may be equal to the area of the main surface 1 c of the piezoelectric ceramic plate 1. The area of the internal electrode 5 here is not the area occupied by the internal electrode but the area inside the outline of the region where the internal electrode is present, and is the area including the cavity and the like existing inside the internal electrode. In addition, a region where no internal electrode exists (so-called margin portion) may exist around a region where the internal electrode exists.

  Also in the first embodiment, as shown in FIG. 3, the average particle diameter D1 of the crystal particles 2 located in the vicinity of the surface gravity center G of the main surface 1c and the crystal particles 2 located in the vicinity of the baked side surfaces (1d, 1e). The average particle diameter D2 is in the range of 0.9 to 1.1 in the ratio of D2 to D1 (D2 / D1).

  For example, when an electronic component having a thickness of 40 mm × 30 mm and a thickness of 40 μm is manufactured using the conventional piezoelectric ceramic plate 1, D2 / D1 is smaller than 0.9, for example, 0.87 or less, and ΔL is 200 μm after baking. Larger or ΔF was larger than 100 μm, and processing was necessary after firing.

  On the other hand, in the case of an electronic component using the piezoelectric ceramic plate 1 of the present embodiment, D2 / D1 is in the range of 0.9 to 1.1. As a result, ΔL after firing of the piezoelectric ceramic plate 1 is 200 μm or less, ΔL / Lc is 1.0% or less, and deformation in the surface direction (xy direction) of the main surface 1 c is reduced. Further, ΔF after firing of the piezoelectric ceramic plate 1 is 100 μm or less, ΔF / Lmax is 0.2% or less, deformation in the thickness direction (z direction) is small, and flatness with small warpage is excellent. Become. Therefore, the electronic component of the first embodiment does not need to be processed after firing. Thus, since the electronic component of this embodiment has few deformations after firing, an electronic component having a desired shape and size can be obtained without being processed after firing, and the manufacturing cost can be reduced. In addition, cracks, chips and the like due to processing can be reduced.

  The electronic component may include three or more piezoelectric ceramic layers 9 and two or more internal electrodes 5.

  FIG. 7 shows a second embodiment of the electronic component, which includes a plate-like substrate 8 and a pair of external electrodes 17 that are alternately connected to the internal electrodes 5. The pair of external electrodes 17 are arranged on the second side surface 1 e facing the piezoelectric ceramic plate 1. A pair of second side faces 1e of the piezoelectric ceramic plate 1 on which the external electrodes 17 are disposed are processed surfaces. External electrodes 17 are disposed on these processed surfaces, and the internal electrodes 5 and the external electrodes 17 are connected. The processed surface is a surface obtained by processing the baked surface, such as a cut surface or a polished surface.

  The processed surface may be the entire pair of second side surfaces 1e of the piezoelectric ceramic plate 1, or may be a part of the second side surface 1e. For example, a portion of the second side surface 1e where the external electrode 17 is disposed may be a processed surface.

  On the other hand, the pair of first side surfaces 1d of the piezoelectric ceramic plate 1 where the external electrode 17 is not disposed are baked surfaces.

  As shown in FIG. 7B, the internal electrode 5 is a partial electrode formed on a part of the piezoelectric ceramic layer 9, and a part of the internal electrode 5 is the second side surface 1 e of the piezoelectric ceramic plate 1. And is connected to the external electrode 17.

  As in the case of the electronic component of FIG. 6, in the second embodiment, the average particle diameter D1 of the crystal particles 2 located in the vicinity of the center of gravity G of the principal surface 1c of the piezoelectric ceramic plate 1 and the vicinity of the baked side surface (1d) The average particle diameter D2 of the positioned crystal particles 2 is in the range of 0.9 to 1.1 in terms of the ratio of D2 to D1 (D2 / D1).

  Also in the electronic component of the second embodiment, ΔL / Lc after firing the piezoelectric ceramic plate 1 is 1.0% or less, and deformation in the surface direction (xy direction) of the main surface 1c is reduced. Further, ΔF / Lmax after firing of the piezoelectric ceramic plate 1 is 0.2% or less, the deformation in the thickness direction (z direction) is small, and the flatness with small warpage is excellent. Thereby, the processing of the first side surface 1d of the piezoelectric ceramic plate 1 can be eliminated, an electronic component having an accurate shape and size can be easily obtained, and the manufacturing cost can be reduced.

  6 and 7, the internal electrode 5 is mainly composed of Ag, and in addition to Ag, Pd may be contained in a range of 40% by mass or less, 35% by mass or less, and further 30% by mass or less. Good.

(Piezoelectric ceramic plate material)
The piezoelectric ceramic plate 1 of the present embodiment preferably has a porosity of 0.6% or less from the viewpoint of denseness. By using the dense piezoelectric ceramic plate 1 as described above, the mechanical loss can be reduced, and the piezoelectric ceramic plate 1 with less deterioration and variation in piezoelectric characteristics is obtained.

As a piezoelectric material constituting the piezoelectric ceramic plate 1 (piezoelectric ceramic layer 9), for example, a lead-based piezoelectric material such as lead zirconate titanate (hereinafter also simply referred to as PZT-based), a material having a bismuth layer structure (SrBi ₄ Ti such as ₄ O _15, SBT-based), barium titanate having a perovskite structure like a non-lead-based piezoelectric material, such as (such as BaTiO _3, BT-based), alkali niobate-based _((KNa) NbO 3, KNN-based) It is done.

In particular, a lead zirconate titanate-based (PZT) -type piezoelectric material containing any one of Zn and Cu and Bi, and an alkali niobate-based ((KNa) NbO ₃ ) containing Li, Ta, and Bi. , KNN) piezoelectric material can be uniformly sintered at a relatively low firing temperature and exhibits excellent piezoelectric properties. In other words, the crystal particles 2 constituting the piezoelectric ceramic plate 1 of the present embodiment are composed of any one of Zn and Cu, and lead zirconate titanate (PZT) crystal particles 2 containing Bi. Alternatively, the ratio (D2 / D1) of D2 to D1 is 0.9 to 1.1 by using crystal particles 2 of an alkali niobate ((KNa) NbO ₃ , KNN) containing Li, Ta, and Bi. It can be a range.

  Such PZT-based crystal particles 2 or KNN-based crystal particles 2 are both composite perovskite compounds. If the crystal particle 2 is a PZT system, it may contain Sb, Ni and Nb in addition to Pb, Zr, Ti, Zn, Cu and Bi as a metal component. Further, at least one of Sr and Ba may be included as necessary. In the case where the crystal particle 2 is a KNN system, Mg, Cu, Fe, Zn, Ti, Zr, Hf, Ge, Sn, and Ce in addition to K, Na, Nb, Li, Ta, and Bi as metal components At least one of them may be included. Further, Sb and Mn may be included as necessary.

(PZT piezoelectric material)
The PZT-based piezoelectric material will be described in detail. In the PZT-based piezoelectric material described above, an amorphous phase containing Li, B, or the like, or a crystal phase (heterophase) other than the PZT-based crystal does not substantially exist at the crystal grain boundary 3. Therefore, the change with time of the insulation resistance and the deterioration of the piezoelectric characteristics due to these residuals are small.

  The PZT-based piezoelectric material is composed of PZT-based crystal particles 2 from the viewpoint of maintaining stable insulation resistance and piezoelectric characteristics, and has a crystal phase other than PZT-based crystals, that is, a crystal phase having low piezoelectric characteristics and insulation resistance. It is preferably not included. A crystal phase other than the PZT crystal (hereinafter referred to as a heterogeneous phase) substantially does not include a heterogeneous phase in a lattice image by a transmission electron microscope (TEM), or X using a cross-sectional Cukα ray. In a line diffraction (XRD) measurement, only the peak derived from a PZT type | system | group crystal | crystallization is recognized, and it says that the peak derived from other hetero phases does not exist substantially.

  In addition, in the X-ray diffraction measurement using Cukα rays, the fact that a peak derived from a different phase other than the PZT crystal does not substantially exist means that the (111) diffraction peak intensity of the PZT crystal is 100. Means that the diffraction peak intensity is 3 or less. The diffraction peak intensity is represented by the length to the peak perpendicular to the tangent line, with tangent lines drawn on both sides of the diffraction peak in the diffraction profile obtained by X-ray diffraction (XRD) measurement. Assuming that the (111) diffraction peak intensity of the PZT crystal is 100, the peak intensity of the crystal phase (heterophase) other than the PZT crystal phase with low piezoelectric characteristics and insulation resistance is the (111) diffraction peak of the PZT crystal. If it is 3 or less with respect to strength, it can be suitably used without greatly affecting the piezoelectric characteristics of the piezoelectric ceramic plate 1.

  Moreover, it is preferable that the PZT-based piezoelectric material does not substantially contain an alkali metal element such as Li or Na and B (boron). When an alkali metal element such as Li or Na and B (boron) are added when firing a PZT-based piezoelectric material at a low temperature, a liquid phase is formed and the sinterability is improved. There is a concern that an amorphous phase or a crystal phase other than the PZT crystal remains in the crystal grain boundary 3 and the insulation resistance is lowered with time or the piezoelectric characteristics are lowered. Note that alkali metal elements such as Li and Na and B (boron) may be inevitably contained as impurities. Therefore, substantially not containing alkali metal elements such as Li and Na and B (boron) means that these elements are not actively added in the manufacturing process of the piezoelectric ceramic plate 1.

  When a PZT-based piezoelectric material is used, the average particle size of the crystal particles 2 in the piezoelectric ceramic plate 1 is preferably 1.0 to 4.0 μm. If the average particle size of the crystal particles 2 is too small, the piezoelectric characteristics are deteriorated. If the average particle size is too large, the hysteresis is increased, and heat is easily generated when driven as an electronic component. By setting the average particle size of the crystal particles 2 in the range of 1.0 to 4.0 μm, it is possible to maintain necessary piezoelectric characteristics and suppress heat generation when driven as an electronic component.

The composition of the PZT-based piezoelectric material is, for example, at least one of a PZT-based first component represented by the following composition formula (1), Bi oxide, and Zn oxide and Cu oxide as necessary. It is represented by a PZT-based second component containing one of these. In the composition formula of the PZT-based first component, M1 represents at least one element of Cu and Ni.
PZT first component:
_{Pb 1-x-y Sr x} Ba y Ti 1-a-b-c (Zn 1/3 Sb 2/3) a (M1 1/3 Nb 2/3) b Zr c O 3 ··· (1)
In the composition formula (1) of the PZT first component, x, y, a, b, and c satisfy the following relational expressions.

0 ≦ x ≦ 0.14,
0 ≦ y ≦ 0.14 (where x + y ≧ 0.04),
0.01 ≦ a ≦ 0.12,
0 ≦ b ≦ 0.015
0.42 ≦ c ≦ 0.58,
Here, the reason why the substitution amount x of Pb with Sr is set to 0 ≦ x ≦ 0.14 is that the Curie temperature can be kept high by replacing a part of Pb with Sr. The reason why the substitution amount y of Pb with Ba is set to 0 ≦ y ≦ 0.14 is that the Curie temperature can be kept high by replacing a part of Pb with Ba, and a high piezoelectric strain constant d ₃₁ can be obtained. Because it can.

Moreover, the reason _{why the} substitution amount a of Ti with (Zn _1/3 Sb _2/3 ) is set to 0.01 ≦ a ≦ 0.12 is that a large piezoelectric strain constant d ₃₁ and a piezoelectric output constant g ₃₁ are obtained. This is because the temperature can be kept high and the dielectric loss can be kept small. When the piezoelectric ceramic plate 1 of the present embodiment is used as a piezoelectric actuator, a large piezoelectric strain constant can be obtained by setting 0.05 ≦ a ≦ 0.12, and 0.01% when used as a piezoelectric sensor. By setting ≦ a ≦ 0.05, a large piezoelectric output constant g ₃₁ can be obtained.

When the substitution amount b of Ti by (M1 _1/3 Nb _2/3 ) is 0 ≦ b ≦ 0.015, the coercive electric field can be increased while suppressing the decrease in the piezoelectric d constant. Ni and Cu are used as M1, but when Cu is used, the piezoelectric ceramic plate 1 having a large coercive electric field can be obtained while maintaining a particularly high piezoelectric d constant, and deterioration of displacement can be suppressed. b is particularly preferably 0.002 ≦ b ≦ 0.01.

PZT has a so-called MPB (Morphotropic phase boundary) region including a boundary where the crystal structure changes depending on the solid solution ratio of PbZrO ₃ and PbTiO ₃ . In MPB, the piezoelectric strain constant shows a maximum value. When the piezoelectric ceramic plate 1 of this embodiment is used as a piezoelectric actuator, this MPB and the composition in the vicinity thereof are used. Since this MPB varies depending on the values of x, y, a, and b, the value of c is a composition range in which MPB can be captured within the composition range of x, y, a, and b.

Moreover, when the mass ratio of the PZT second component to 100% by mass of the PZT first component is expressed as α%, α is 0.1 or more and 2.0 or less. Note that α is the total amount of Bi, Zn, and Cu, which are PZT-based second components, converted to oxides (Bi ₂ O ₃ , ZnO, and CuO), respectively, but is a composite oxide of Zn and Bi (for example, Bi ₃₈ ZnO ₅₈ , Bi ₃₈ ZnO ₆₀ , Bi ₄₈ ZnO ₇₃ and BiZnO) and Cu and Bi composite oxides (for example, CuBi ₂ O ₄ , Cu ₂₁ Bi ₅₂ O ₁₀₀ , Cu _0.62 Bi _7.38 O _11.69). And BiCuO, etc.).

  By setting the mass ratio α (%) of the PZT second component (Zn oxide, Cu oxide and Bi oxide) to the PZT first component in the range of 0.1 ≦ α ≦ 2.0, PZT The system second component forms a liquid phase during firing and wets the crystal particles 2 that are PZT crystals. At this time, even if the composition of the PZT-based second component is slightly different, the difference in the liquid phase generation temperature is small, the liquid phase is generated in a short time, the sinterability is improved, and the entire ceramic is sintered uniformly. . As a result, D2 / D1 is in the range of 0.9 to 1.1, that is, the average grain size of the crystal grains 2 is uniform regardless of the measurement position, and the plate-like piezoelectric ceramic plate 1 having a small thickness and a large area. But deformation can be reduced. This is because, after the piezoelectric ceramic plate 1 is sintered, the PZT-based second component (Zn, Cu and Bi) that has formed a liquid phase is dissolved in the PZT-based crystal.

(KNN piezoelectric material)
The above-described KNN-based piezoelectric material will be described in detail. When the above-described KNN-based piezoelectric material is used, the average particle size of the crystal particles in the piezoelectric ceramic plate 1 is preferably 0.3 to 2.0 μm. If the average particle size of the crystal particles is too small, the piezoelectric characteristics are deteriorated. If the average particle size is too large, the hysteresis is increased, and heat is easily generated when the electronic component is driven. By setting the average particle size of the crystal particles in the range of 0.3 to 2.0 μm, it is possible to maintain necessary piezoelectric characteristics and suppress heat generation when driven as an electronic component.

The composition of the KNN piezoelectric material includes, for example, a KNN first component represented by the following composition formula (2), a Bi oxide, an oxide of M2, and an oxide of M3 as necessary. It is represented by the KNN second component contained.
KNN first component:
_{{(K 1-d Na d} ) 1-e Li e} f (Nb 1-g-h Ta g Sb h) O 3 ··· (2)
In the composition formula (2) of the KNN first component, d, e, f, g, and h satisfy the following relational expressions.

0.50 ≦ d ≦ 0.54,
0.02 ≦ e ≦ 0.06,
0.980 ≦ f ≦ 1.005
0.04 ≦ g ≦ 0.15
0 ≦ h ≦ 0.10,
KNN has a perovskite structure, and there is a so-called MPB (Morphotoropic Phase Boundary) region including a boundary where the crystal structure changes depending on the solid solution ratio between KNbO ₃ and NaNbO ₃ . In MPB, the piezoelectric strain constant shows a maximum value.

  That is, in the composition formula (2) of the KNN first component, the piezoelectric constant can be increased by substituting Na with a part of K in the range of 0.50 ≦ d ≦ 0.54. .

  Moreover, e can be made 0.02 or more, and Li can be introduced into the A site to improve the sinterability of the piezoelectric ceramic plate 1, and e should be in the range of 0.02 ≦ e ≦ 0.06. Thus, the piezoelectric constant can be increased.

  The reason why g is in the range of 0.04 ≦ g ≦ 0.15 is that the piezoelectric constant can be increased by replacing part of Nb with Ta. Note that when g exceeds 0.15, the piezoelectric constant decreases and the Curie temperature may decrease.

  The reason why h is in the range of 0 ≦ h ≦ 0.10 is that sinterability can be improved by substituting a part of Nb with Sb as necessary. In addition, when h exceeds 0.10, there exists a possibility that sinterability may fall.

  f is in the range of 0.980 ≦ f ≦ 1.005. This is because if the A site atom of the perovskite structure is less than 0.980 with respect to the B site atom or excessively contained exceeding 1.005, the piezoelectric characteristics may be deteriorated.

The KNN second component is represented by the following composition formula (3).
KNN second component:
Bi _i (M2 _1-j M3 _j ) O ₃ (3)
In the composition formula (3) of the KNN second component, i and j satisfy the following relational expression.

2/3 ≦ i ≦ 1,
1/3 ≦ j ≦ 2/3,
Further, when the molar ratio of the KNN-based second component to the total amount of the KNN-based first component and the KNN-based second component is β, β is 0.001 or more and 0.005 or less.

  The KNN second component constitutes a Bi composite oxide having a composite perovskite structure. Since Bi has 6s2 lone electron pairs, it has a large distortion in the crystal structure. By introducing a predetermined amount of this Bi composite oxide into the KNN-based first component, strain is introduced into the crystal structure of potassium niobate / sodium niobate, polarization increases, and piezoelectric characteristics are improved. At the same time, the temperature dependence of the piezoelectric characteristics can be reduced. In addition, since a compound containing Bi generates a liquid phase at a relatively low temperature, an oxide serving as a KNN second component for forming a Bi composite oxide is introduced as an auxiliary agent into the synthetic powder of the KNN first component. By doing so, the firing temperature of the piezoelectric ceramic is lowered, the sinterability is improved, and the entire porcelain can be sintered uniformly.

  M2 in the KNN second component is at least one selected from the group consisting of Mg, Cu, Fe and Zn, and M3 is composed of Nb, Ta, Sb, Ti, Zr, Hf, Ge, Sn and Ce. It is at least one selected from the element group. By selecting M2 and M3 from such an element group, even if the piezoelectric constant is large, the temperature dependence of the piezoelectric characteristics is small, and high and stable piezoelectric characteristics can be obtained over a wide temperature range.

  Here, i is in the range of 2/3 ≦ i ≦ 1. By setting i in such a range, the Bi composite oxide can be incorporated into the KNN crystal particles without excess or deficiency. If i is smaller than 2/3, the piezoelectric characteristics may be deteriorated. If i is larger than 1, excessive Bi may remain at the grain boundary, and the insulating property of the piezoelectric ceramic plate 1 may be deteriorated. There is.

  M2 is at least one selected from the group consisting of Mg, Cu, Fe and Zn, and M3 is at least selected from the group consisting of Nb, Ta, Sb, Ti, Zr, Hf, Ge, Sn and Ce. One type. These have an ionic radius comparable to that of Nb in a six-coordinate state with oxygen.

  j is in the range of 1/3 ≦ j ≦ 2/3. By setting j in such a range, the ratio of M2 and M3 can be within the range of the stoichiometric ratio. If the ratio of M2 and M3 deviates significantly from the stoichiometric ratio, oxygen vacancies are formed, and the piezoelectric characteristics may be deteriorated.

  When M3 is an element that becomes a pentavalent ion, that is, at least one of Nb, Ta, and Sb, i + j is set to 4/3, so that M2 and M3 are stoichiometrically. It can be within the range of the ratio, and is preferable. In addition, when M3 is an element that becomes a tetravalent ion, that is, at least one of Ti, Zr, Hf, Ge, Sn, and Ce, by reducing j to 1/2, M2 and M3 Can be within the stoichiometric range.

  In this way, by introducing the composite perovskite structure having a large strain of the Bi composite oxide which is the KNN second component into the KNN first component perovskite structure, the piezoelectric constant is increased and the temperature dependence of the piezoelectric characteristics is increased. Can be small. At the same time, the firing temperature of the piezoelectric ceramic is lowered, the sinterability is improved, and the entire porcelain can be sintered uniformly. As a result, D2 / D1 is in the range of 0.9 to 1.1, that is, the average grain size of the crystal grains 2 is uniform regardless of the measurement position, and the plate-like piezoelectric ceramic plate 1 having a small thickness and a large area. But deformation can be reduced. This is because after the piezoelectric ceramic plate 1 is sintered, the KNN second component (the component forming the Bi composite oxide) that has formed a liquid phase is dissolved in the KNN crystal.

The molar ratio β of the KNN second component to the total amount of the KNN first component and the KNN second component is 0.001 ≦ β ≦ 0.005. By setting β in such a range, moderate strain is introduced into the perovskite structure of potassium niobate and sodium, and the piezoelectric constant can be increased. If β is smaller than 0.001, the desired effect cannot be obtained. If β is larger than 0.005, the introduced strain becomes too large, and the piezoelectric characteristics are deteriorated.

Furthermore, the KNN piezoelectric material may contain 0.50 parts by mass or less of Mn in terms of MnO _{2 with} respect to 100 parts by mass of the total amount of the KNN first component and the KNN second component. Thereby, the piezoelectric ceramic plate 1 can be made denser, and the piezoelectric constant can be further increased.

(Manufacturing method)
The piezoelectric ceramic plate 1 of the present embodiment can be manufactured as follows. For example, when a PZT-based piezoelectric material is used, a mixed raw material of a calcined powder containing a PZT-based first component and a powder containing a PZT-based second component (Zn oxide, Cu oxide, and Bi oxide) A green sheet is obtained by molding by a known sheet molding method. When a KNN piezoelectric material is used, a calcined powder containing a KNN first component and a powder containing a KNN second component (Bi oxide, M2 oxide, and optionally M3 oxide) The mixed raw material is formed by a known sheet forming method to obtain a green sheet.

  When producing an electronic component, an internal electrode paste is applied to the green sheet to form an internal electrode pattern. A plurality of green sheets on which internal electrode patterns are formed are stacked, and finally a green sheet on which no internal electrode patterns are formed is stacked to produce a plate-shaped substrate molded body. In the case of, firing is performed at 900 to 1050 ° C. in the atmosphere, and in the case of a KNN material, firing is performed at 1000 to 1150 ° C. in the atmosphere.

  In such a manufacturing method, in the case of a PZT-based piezoelectric material, even if firing at a low temperature of 900 to 1050 ° C., the PZT-based second component (Zn oxide, Cu oxide and Bi oxide) is, for example, about 750 ° C. A liquid phase is formed at a low temperature, and the crystal particles 2 of the PZT crystal can be sufficiently wetted at a temperature lower than the firing temperature. Also, in the case of a KNN-based piezoelectric material, by firing at 1000 to 1150 ° C., the KNN-based second component containing Bi forms a liquid phase at a low temperature, and KNN-based crystal particles are formed at a temperature lower than the firing temperature. Can be wet enough. As a result, the sinterability of the piezoelectric ceramic plate 1 can be improved, the entire piezoelectric ceramic plate 1 contracts substantially uniformly, and the elements of the second components are dissolved in the crystals of the first components after sintering. .

  As shown in FIG. 2, the sintered piezoelectric ceramic plate 1 is mainly composed of crystal particles 2 and D2 / D1 is in the range of 0.9 to 1.1.

  A more specific production method will be described. First, a calcined powder containing a PZT-based one component is prepared for a PZT-based piezoelectric material, and a calcined powder containing a KNN-based first component is prepared for a KNN-based piezoelectric material.

Specifically, for example, in the case of a PZT-based piezoelectric material, PbO, ZrO ₂ , TiO ₂ , ZnO powders as raw materials, and Sb ₂ O ₃ , CuO, NiO, Nb ₂ O ₅ , SrCO _{3 as} necessary. And BaCO ₃ powders are weighed and mixed. In the case of a KNN-based piezoelectric material, weighed and mixed Na ₂ CO ₃ , K ₂ CO ₃ , Li ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ powders as necessary and Sb ₂ O ₃ powder as required To do.

Next, this mixture is dehydrated and dried, and then calcined at a maximum temperature of 850 to 950 ° C. for the PZT piezoelectric material and 900 to 1000 ° C. for the KNN piezoelectric material for 1 to 3 hours. In this way, a calcined powder composed of a PZT-based first component and a calcined powder composed of a KNN-based first component are obtained. The obtained calcined powder is pulverized again with a ball mill or the like so that, for example, the average particle diameter D ₅₀ is in the range of 0.3 to 0.7 μm.

Next, PZT-based calcined powder is weighed and mixed with PZT-based second component (Zn oxide, Cu oxide, and Bi oxide, such as ZnO, CuO, and Bi ₂ O ₃ ) powders. The KNN-based calcined powder is weighed and mixed with the powder of the second KNN-based component (Bi oxide, M2 oxide, and optionally M3 oxide). Each of these second components may be added to the calcined powder, or a mixed powder obtained by mixing only the second component in advance may be added to the calcined powder.

Alternatively, the second component may be calcined to synthesize a composite oxide of the second component (hereinafter referred to as a second composite oxide) and added to the calcined powder. When synthesizing the PZT-based second composite oxide, a predetermined amount of Zn oxide, Cu oxide and Bi oxide are mixed, and the resulting mixture is dehydrated and dried, and then, for example, 600 to 720 in air. What is necessary is just to calcine at 1 degreeC for 1-3 hours. The average particle diameter D ₅₀ of the second component may be in the range of 0.3 to 0.7 μm, and is adjusted by using a ball mill or the like so as to be smaller than the average particle diameter (D ₅₀ ) of the calcined powder. It is preferable to do.

  The calcined powder to which the second component has been added is mixed with a binder and then formed into a desired shape using a known forming method such as press forming or a sheet forming method such as a doctor blade method.

  The plate-like substrate 8 and electronic parts are produced as follows. An internal electrode paste is applied to the formed green sheet to form an internal electrode pattern. A required number of green sheets on which internal electrode patterns are formed are stacked, and finally, green sheets on which no internal electrode patterns are formed are stacked to produce a plate-shaped substrate molded body.

  The produced compact is fired at 900 to 1050 ° C. for PZT-based material and 1000 to 1150 ° C. for KNN-based material in the air, so that the piezoelectric ceramic plate 1 and the plate-like substrate 8 are obtained.

  Even if the piezoelectric ceramic plate 1 of this embodiment is fired at a low temperature of 900 to 1050 ° C. (PZT-based material) or 1000 to 1150 ° C. (KNN-based material), the second component forms a liquid phase and crystal particles 2 , So that the sinterability is high and the porosity is 0.6% or less.

  Further, the second component generates a liquid phase at a temperature sufficiently lower than the firing temperature (in the case of the PZT second component, about 750 ° C.), and the entire porcelain starts to sinter uniformly during firing. Therefore, the average particle diameter of the crystal particles 2 located in the vicinity of the baked side surface with respect to the average particle diameter D1 of the crystal particles 2 located in the vicinity of the center of gravity G of the principal surface 1c is uniform regardless of the measurement position. The ratio (D2 / D1) of the particle diameter D2 is in the range of 0.9 to 1.1, and deformation of the piezoelectric ceramic plate 1 is less likely to occur during the sintering process even if the thickness is thin.

  On the other hand, for example, when Li or B that forms a liquid phase is added in order to fire a PZT crystal at a low temperature, it can be fired at a low temperature, but it is difficult to uniformly sinter the entire porcelain. The piezoelectric ceramic plate 1 is likely to be warped or deformed.

  The piezoelectric ceramic plate 1 of the present embodiment is suitably used for an electronic component having a thickness of 150 μm or less, particularly 50 μm or less.

The piezoelectric ceramic plate 1 can be used as various electronic components such as a ceramic filter, an ultrasonic applied vibrator, a piezoelectric buzzer, a piezoelectric ignition unit, an ultrasonic motor, a piezoelectric fan, a piezoelectric sensor, and a piezoelectric actuator. For example, a piezoelectric actuator uses a displacement or force generated through a piezoelectric phenomenon as a mechanical drive source, and is one of those that have recently attracted attention in the field of mechatronics. Piezoelectric actuators are solid-state elements that use the piezoelectric effect and consume less power, have a faster response speed, have a larger amount of displacement, and generate heat compared to conventional electromagnetic actuators that have a configuration in which a coil is wound around a magnetic material. It has excellent features such as small amount, small size and weight. In particular, a laminated piezoelectric actuator capable of obtaining a larger displacement and generating force at a lower voltage has been put to practical use as an acoustic component such as an autofocus for a camera for opening / closing a fuel injection valve of an in-vehicle injector and a piezoelectric speaker.

PbT, ZrO ₂ , TiO ₂ , ZnO, Sb ₂ O ₃ , SrCO ₃ , BaCO ₃ , CuO, and Nb ₂ O ₅ powders having a purity of 99.5% were used as PZT-based raw material powders. The PZT-based first component, the composition formula _{(1) (Pb 1-x} -y Sr x Ba y Ti 1-a-b-c (Zn 1/3 Sb 2/3) a (M1 1/3 Nb 2 / ₃ ) It was weighed so as to have the composition shown in Table 1 in _b Zr _c O ₃ ), and wet mixed in a ball mill for 24 hours. M1 is Cu or Ni. Next, this mixture was dehydrated and dried, then calcined at 920 ° C. for 3 hours, and the calcined product was wet-ground again with a ball mill for 24 hours to obtain a calcined powder having a D ₅₀ of 0.5 to 0.7 μm. .

Thereafter, the additive shown in Table 1 having a D50 of _0.5 to 0.7 μm was added in an amount (% by mass) shown in Table 1 as a ratio to 100% by mass of the PZT-based first component, and an organic binder was added thereto. Were mixed.

As the KNN-based raw material powder, each of the 99.9% pure Na ₂ CO ₃ , K ₂ CO ₃ , Li ₂ CO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , and Sb ₂ O ₃ powder is used. the first component is a composition of Table 2 in the formula _{(2) ({(K 1} -d Na d) 1-e Li e} f (Nb 1-g-h Ta g Sb h) O 3) And wet mixed in a ball mill for 16 hours. Next, this mixture was dehydrated and dried, and then calcined at 1000 ° C. for 3 hours, and the calcined product was wet-ground again with a ball mill for 16 hours to obtain a calcined powder having a D ₅₀ of 0.3 to 0.7 μm. .

Thereafter, the additives shown in Tables 2 and 3 having D ₅₀ of 0.3 to 0.7 μm (Bi ₂ O ₃ , MgCO ₃ , ZnO, CuO, Fe ₂ O ₃ , TiO ₂ , SnO ₂ , ZrO ₂ , HfO ₂₎ , Ce ₂ O ₃ , GeO _2, and MnO ₂ ) are added in the molar ratio to the total amount of the KNN first component and the KNN second component in the amounts shown in Tables 2 and 3, Organic binder was mixed.

  A green sheet having a thickness of 25 μm was produced by the doctor blade method using the obtained mixed raw material. An internal electrode paste containing Ag and Pd is screen-printed on the entire surface of the produced green sheet, and a green sheet on which the internal electrode paste is not printed is stacked on the printed surface side of the green sheet on which the internal electrode paste is printed. Thus, a plate-like substrate molded body was produced. The mass ratio of the metal components of the internal electrode paste was Ag: Pd = 7: 3.

  After removing the binder of the produced plate-like substrate molded body, it was fired in the air under the firing conditions shown in Tables 1 to 3 and cooled to obtain a plate-like substrate.

The thickness of the obtained plate-like substrate was 42 μm (the thickness of the piezoelectric ceramic layer was 20 μm), and the main surface was a rectangular plate having a size of 120 mm × 40 mm (area 4800 mm ² ).

  An external electrode was formed on one surface (main surface) of the obtained plate-like substrate by baking an Ag paste, and polarization treatment was performed to obtain a laminated piezoelectric actuator that was an electronic component for evaluating piezoelectric characteristics. .

The average particle size of the piezoelectric ceramic layer was determined by taking a photograph of the main surface, which is a baked surface, using a scanning electron microscope (SEM) and subjecting the photograph to image processing. In the image processing, the equivalent circle diameter of the cross-sectional area obtained from the contour of the crystal particle was regarded as the diameter of the crystal particle. The measurement position of D1 was the center of gravity of the main surface of the plate-like substrate. The measurement position of D2 was a position where the distance Lf from the surface centroid on the diagonal of the main surface was 95% of the distance Lo from the surface centroid to the baked side surface. The magnification of the SEM photograph was 3000 times. The calculated D1, D2, and D2 / D1 are shown in Tables 1-3.

  The porosity of the piezoelectric ceramic layer is obtained by mirror-polishing the cross section of the plate-like substrate, observing the polished surface using a scanning electron microscope (SEM), and processing the photograph of the piezoelectric ceramic layer. It was. For the density of the piezoelectric ceramic layer, the bulk density of the plate-like substrate was determined by the Archimedes method, and the bulk density was regarded as the density of the piezoelectric ceramic layer. The density and porosity are shown in Tables 1-3.

  When the composition of the plate substrate was confirmed by ICP emission spectroscopic analysis, the composition of the piezoelectric layer coincided with the composition at the time of preparation within the range of error.

  In the deterioration test of the insulation resistance of the piezoelectric layer, a DC electric field of 2 kV / mm was applied to the electronic component in a constant temperature bath at 85 ° C. The insulation resistance of the electronic component at 85 ° C. was measured and converted into volume resistivity, and the volume resistivity at the initial stage of the test and after 100 hours is shown in Tables 1 to 3.

Regarding piezoelectric characteristics, after aging treatment was performed on a polarized electronic component at 120 ° C., a 12 × 3 mm test piece was cut out, and a DC voltage was applied to the two surface electrodes formed on the upper and lower surfaces of the test piece for polarization. It performs processing, as described in seeking tables 1-3 the piezoelectric constant d ₃₁ of the electronic component by measuring the vibration mode in the longitudinal direction.

  The deformation of the piezoelectric ceramic plate was evaluated as a ratio (ΔL / Lc). The length of the piezoelectric ceramic plate was measured using a CNC image measuring device. Moreover, flatness was measured with a laser three-dimensional measuring device (manufactured by Keyence Corporation), and ΔF was calculated. Further, ΔF / Lmax was determined with Lmax as the length of the diagonal line of the main surface. Tables 1 to 3 show ΔL / Lc, ΔF, and ΔF / Lmax of the piezoelectric ceramic plate.

  From Tables 1 to 3, Sample No. In 1 to 6 and 9 to 24, D2 / D1 was within a range of 0.9 to 1.1, and there was almost no difference in the average grain size of the crystal grains between the vicinity of the side surface of the grilled surface and the vicinity of the center of gravity. Further, the deformation is small, ΔL / Lc is 1% or less, and ΔF / Lmax is 0.2% or less, which indicates that the processing after firing is unnecessary or can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric ceramic board 1c ... Main surface 1d ... 1st side surface 1e ... 2nd side surface 2 ... Crystal grain 5 ... Internal electrode 7 ... External electrode 8 ... Plate Substrate 9 ... piezoelectric ceramic layer 10 ... surface electrode 11 ... via-hole conductor 17 ... external electrode

Claims (10)

Having a plurality of crystal grains,
Comprising a pair of main surfaces and a side surface located between the main surfaces;
At least one of the side surfaces is a baked surface;
When the average particle diameter of the crystal particles located in the vicinity of the center of gravity of the main surface is D1, and the average particle diameter of the crystal particles located in the vicinity of the side surface that is the baked surface is D2, A piezoelectric ceramic plate having a D2 ratio (D2 / D1) in a range of 0.9 to 1.1.   The piezoelectric ceramic plate according to claim 1, wherein at least one of the pair of main surfaces is a baked surface.   The piezoelectric ceramic plate according to claim 1 or 2, wherein the D1 and the D2 are in a range of 0.3 to 4.0 µm. The piezoelectric ceramic plate according to any one of claims 1 to 3, wherein an area of the main surface is 360 mm ² or more. The piezoelectric ceramic plate according to claim 4, wherein an area of the main surface is 1000 mm ² or more.   The piezoelectric ceramic plate according to claim 1, wherein the thickness is 150 μm or less.   A plate-like substrate having an internal electrode in the piezoelectric ceramic plate according to claim 1. A surface electrode disposed on the surface of the plate-like substrate according to claim 7;
An electronic component comprising: a via-hole conductor connected to the internal electrode and extending in the thickness direction of the piezoelectric ceramic plate and drawn to the surface of the plate-like substrate.   The electronic component according to claim 8, wherein all of the side surfaces are baked surfaces. While comprising the plate-like substrate according to claim 7 and an external electrode connected to the internal electrode,
The electronic component, wherein the piezoelectric ceramic plate includes the side surface having a processed surface, and the external electrode is disposed on the processed surface.